Development Of Metro Regenerative Braking Energy Feed Converter Based On Three-level Structure

As of the end of 2018,36 cities in China have opened subways,operating a mileage of5494.9 kilometers.The distance between ground stations is short,the start and stop are frequent,and the regenerative energy in the braking process reaches 30%-40% of the total energy.In recent years,domestic subways have begun to use energy-feeding devices to send regenerative energy back to the medium-voltage AC grid,which has played a very good economic and social efficiency.The regenerative braking energy storage device stores the regenerative energy in the super capacitor or other energy storage medium when the train brakes,and then sends it to the DC power grid for train traction when the train is traction.Compared with energy-feeding devices,regenerative braking energy storage devices can not only use regenerative braking energy,but also have a good supporting effect on AC and DC power grids.This paper focuses on the research of metro energy storage converters based on supercapacitor media and the development of engineering application of energy storage converters.The main work is as follows:Topology and modeling analysis of energy storage converters.The switch state and current flow path of the three-level bidirectional DC / DC main circuit topology in Buck operating mode at D <0.5 and D> 0.5 are analyzed in detail,and the relationship between input and output voltage is obtained.The state-space averaging method was used to model and analyze the main circuit topology of the converter in Buck operation mode D <0.5 and Boost operation mode D> 0.5 respectively,and a mathematical model of the supercapacitor energy storage system was established;The established mathematical model of the energy storage system uses a double closed-loop control structure based on the voltage outer loop of the grid voltage and the current inner loop of the inductor current.The system performance before and after compensation is compared and analyzed,and the control effect of the double loop controller is verified by simulation.Control strategy of energy storage converter.According to the proposed dual-loop controller structure,the control strategy of the supercapacitor energy storage system is analyzed.The PWM pulse generation principle of interleaved modulation mode is used to drive the four-way power unit,and a simulation is made to compare the grid-side waveforms with and without interleaved modulation strategy.From the SOC state of the super capacitor and the design of the current regulator,the control strategy is studied.A dynamic adjustment strategy based on the no-load voltage of the contact network is proposed.Control Strategy.Finally,the proposed control strategy was simulated to verify the feasibility of the control strategy.Main circuit design of energy storage converter.The overall parameters of the supercapacitor energy storage system are designed.According to the design requirements of the capacitor voltage and inductor current ripple,the parameters of the voltage equalizing capacitor and the output side filter inductor are calculated;the capacity configuration of the super capacitor is based on the energy storage of the device and the SOC of the super capacitor;for the FF600R17ME4＿B11 IGBT of Infineon According to the parameter manual,the power loss of the device and the junction temperature of the device are calculated.Finally,the correctness of the parameters of the capacitor and inductance device is verified by simulation.Experiment and test of energy storage converter.The prototype of the supercapacitor project and the debugging platform were introduced,and the test method of the "1 to 2" supercapacitor energy storage system absorption device was proposed according to the situation of the debugging site.Finally,part of the test results of the type test are introduced,and the feasibility of the control strategy of the energy storage system and the technical specification of the device itself are successfully verified on the engineering prototype equipment.Based on the supercapacitor energy storage project cooperated by enterprises,this paper completed the modeling analysis and controller design of the three-level bidirectional DC /DC converter structure;the control algorithm of the system and the capacitance of the main circuit,The parameters of the inductor and the power device were calculated,and the correctness of the control algorithm and main circuit parameters were verified by simulation.Finally,the equipment type test was passed on the engineering prototype to verify the overall scheme and control algorithm of the system.